The present invention relates to surface-active compositions having a polyvalent action. More particularly, the present invention relates to surface-active compositions which allow not only treatment of oil-polluted water surfaces, but also protection and cleaning of beaches.
It is well known that, when oil is discharged into water, particularly into sea water, the oil comes up to the surface and forms a continuous film or slick which tends to continuously spread. This film of oil is undesirable because it represents a barrier to the transfer of oxygen and light from the atmosphere to support marine life. Moreover, these films of oil may reach and pollute the beaches.
Various techniques have been suggested for solving the oil contamination problem. For example, it has already been proposed to contact this oil film with a dispersing composition containing detergents in order to emulsify the oil with the water and to disperse the continuous oil fim in the form of small droplets. The continuous oil film is then broken, and there is again a transfer of oxygen and light from the atmosphere. However, this technique is not always suitable, particularly when the oil forming the film is highly viscous. Moreover, this dispersion technique requires high energy mixing, which is furnished by either artificial or natural agitation. It is clear that such a technique is not very efficient on a calm sea.
It has been also suggested to use oil collecting compositions, which are poured at the periphery of the oil slick in order to surround it and to avoid it from spreading anymore. One characteristic of these compositions resides in their spreading force which must be higher than that of the oil. This technique of contraction of oil slicks allows a substantially complete removal of the oil by the usual mechanical means. This technique is thus suitable on a calm sea, since no additional energy is required.
However, these oil collecting compositions, which are often in the form of a monolayer solid film of a surface-active agent, are efficient only during a limited period of time, which generally does not exceed 4 hours, and which depends on the solubility of the composition in the oil which must be repelled. After that period of time, the protective barrier breaks at several places, and the oil slick spreads again. In order to remedy this drawback, it has been suggested to introduce the surface-active agent in a hydrocarbon vehicle in order to form a multilayer liquid film of surface-active agent, which more quickly spreads and thus increases the contraction of the oil slick. However, a liquid film which has no support may also spread in a direction opposite to that where it must act.
Moreover, in the scope of beach protection, the composition to be used must at least form a solid film, in order not to penetrate into the sand and also to avoid the impregnation of the sand by the pollutant oil.
Therefore, a surface-active composition with polyvalent action should fulfill the following conditions in order to be efficient on solid substrates as well as on liquid substrates:
form at least a multilayer liquid film,
form at least a solid film having a reduced solubility in the oil to be treated, this solid film acting as a support for the liquid film,
have a spreading force higher than 40 dyne/cm in order to be efficient as an oil collecting composition,
have a sufficient emulsifying power to emulsify the oil, either when the composition is poured onto the oil slick, or when the oil slick comes onto the film formed on the beach,
be handleable at low temperatures,
have a flash point higher than 80.degree. C., and
be biodegradable and non-toxic.
Up until now, none of the proposed compositions fulfills all these conditions.